In bioscience-related fields, researchers are often confronted with the problem of cryopreservation of biological samples. There are various types of biological samples, and in terms of physical states, the samples may be classified into gaseous samples, for example, expired air; liquid samples, for example, body fluids such as blood, urine, cerebrospinal fluid, tears, and saliva; and solid samples, for example, various biological tissues. Apart from that, the cryogenic freezing method is used in many fields such as agriculture, chemical engineering, archaeology and geological prospecting to preserve various precious sample data.
In the field of bioscience, when a solid tissue sample needs to be preserved, a common method at present is to place the tissue into a cryogenic vial for cell cryopreservation, label the cryogenic vial and then put the cryogenic vial into a refrigerator at −80 degrees centigrade, or directly place the tissue into liquid nitrogen for cryopreservation. Another method is to place the tissue on a metal cryogenic tray, and then add an opti-mum cutting temperature compound (OCT) or a shaping agent of another type dropwise around the specimen, where the shaping agent is generally liquid at a normal temperature, and becomes solid in a cryogenic environment. The function of the shaping agent is to protect the specimen from air drying and deformation, and guarantee the isolation of the specimen, and more importantly, the shaping agent can carry the specimen when operations such as freezing sectioning are performed on the specimen in the future. In the latter method, to make the shape of the embedded sample regular, some people use a plastic apparatus of a specified shape for shaping.
A disadvantage of the existing embedding means lies in that: after a sample which is directly cryopreserved by using a cell cryogenic vial is taken out, it needs to be re-embedded before use; and if the shape and size are not suitable, it is extremely difficult to make adjustment in a freezing condition.
After samples preserved using the foregoing two methods are taken out, no unique specimen identifier can be reserved on the surface of the sample. Once a misoperation occurs, the samples are easily confused with each other; the samples are no longer associated with sample-containing sealed bags and cryogenic vials that carry the sample information identifiers; and it is difficult to restore the association, causing the samples to be confused. Such a risk causes a disastrous consequence for subsequent use and results in disuse of the samples.
In addition, the current embedding operation method is relatively complex, where operations need to be performed on each sample separately, rather than operation in batches, which is time-consuming and energy-consuming, causes a waste of embedding materials, is difficult to standardize, and is not good for recycling of samples or the dynamic integration with a modern sample repository management system.
Secondly, an OCT-embedded specimen has an irregular shape, which makes regular placement and storage difficult; the OCT-embedded specimen occupies large refrigeration space, and a large amount of energy and resources are consumed to maintain a low temperature.
In practical application, for a layered tissue having envelope, epithelium and deep tissue structures, it is generally necessary to cut off a section from which structures of several layers can be seen at the same time, and the tissue direction thereof needs to be identified during operations such as slicing. For example, human skin has a cuticle surface exposed to air, and also has a subcutaneous tissue in another direction. During practical application, layers from the outside to the inside need to be observed at the same time, and if a section parallel to the surface of the skin is used mistakenly, indexes that need to be observed and studied cannot be obtained. However, after the opaque shaping agent is used for embedding, the internal structure is unrecognizable.
An auxiliary shaping device is used at present, which slightly improves the shape, but still fails to implement the function of providing an inseparable label on a specimen, and still fails to avoid the prominent problems of misoperation on specimens, confusion between specimens, and the waste of specimens.
An operation environment of OCT embedding is generally a cold cavity of a freezing microtome, a cryogenic refrigerator or a liquid nitrogen cup placed in a room-temperature environment. The cold cavity of the freezing microtome has an irregular shape and small space, which makes the operation extremely inconvenient. When the operation is performed in the cryogenic refrigerator, the refrigerator needs to be open and closed repeatedly, which is not only inconvenient but also very harmful to the refrigerator. The liquid nitrogen refrigeration involves dangerous and complex operations, and also wastes a large amount of liquid nitrogen resources.